Dump Point Safet

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Dump Point Safety

• Prepared by
• Mine Waste and Geotechnical Engineering Division
• Pittsburgh Safety and Health Technology Center
• Mine Safety and Health Administration

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Trucks dump near the edges of stockpiles and
spoil piles thousands of times a day in the
mining industry.
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In the 1990s, 25 miners died when their trucks
went over the edge at dump points...
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Point where truck went over edge
Pile material at its normal angle of repose here
In this accident the pile was 70 feet high pile.
Where the truck went over the edge, the pile had
been loaded out and made steeper than the
materials normal angle of repose. This is a
common feature in many dump-point accidents.
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In this fatal accident, the pile was only 20 feet
high - so its not just the higher piles that you
need to be concerned with...
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• Remember that in a stockpile or spoil pile, the
  material is
• loosely placed
• in relatively thick layers and
• at the materials angle of repose.

As a result, the edge of the pile is barely
stable.
STOCKPILE OR SPOIL PILE

• By contrast, a highway embankment would be
  constructed
• in thin, well compacted layers and
• with a relatively flat outer slope.

These differences illustrate why heavy equipment
must be operated with great caution near the edge
of a stockpile or spoil pile.
HIGHWAY EMBANKMENT
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Another important point is that in a typical haul
truck like this one, two-thirds of the loaded
weight is on the rear axle. A 50-ton capacity
truck might have a gross weight of about 90 tons
when loaded. Two-thirds of that weight, or 60
tons, would be on the rear axle as the truck
backs near the edge of a pile.
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Dump-Point Practices

• Maintain adequate berms

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The heavy weight of the truck acting near the
edge of the pile shows why having an adequate
berm is so important.

• The berm must serve the functions of
• Providing the truck driver with a good visual
  indicator of the location of the edge of the
  pile
• Providing restraint to the vehicle from going
  over the edge.

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As illustrated here, another important function
of the berm is to have a wide enough base to keep
the heavy loading on the rear tires from getting
too close to the edge of the pile - where the
material could give way.
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Dump-Point Practices

• Maintain adequate berms
• Prior to dumping, check the dump area for cracks
  and other potential problems.

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Cracks are a warning sign of an unstable slope.
Equipment operators need to be alert for the
presence of tension cracks. A crack is an
indication that the slope has moved. If the
material is having trouble holding up its own
weight, the added weight of a haul truck may
cause the material to slide.
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Dump short of cracks near the edge of a slope or
of areas where the berm is not at least
axle-height. Mark or barricade these areas to
prevent others from being exposed to hazardous
conditions. Correct the situation by carefully
pushing down the potentially unstable material
and establishing an adequate berm...
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Preferably cracked or unstable material is pushed
down using a track-mounted piece of equipment, as
shown here.
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Some operations drive left on piles so that on
the approach the driver is in a better position
to observe the dump area and to check for cracks
or for an inadequate berm.
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Dump-Point Practices

• Maintain adequate berms
• Prior to dumping, check the dump area for cracks
  and other potential problems.
• Dont dump above an area where the pile has been
  loaded-out, or otherwise made steeper than the
  materials normal angle of repose.

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Loading out from the toe of stockpiles removes
material that was supporting the slope, makes the
remaining slope steeper and less stable, and can
undercut the berm at the top of the pile.
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With the pile loaded out and the berm undercut,
its obvious that it would be highly dangerous to
back a haul truck near this area...
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Yet conditions like these that have been involved
in many of the accidents. In a spoil pile, a
condition similar to this could be created by a
slide below the dumping point.
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If there is uncertainty about the safety of a
dump point for any reason --

• Dump short and push the material over, or
• Dump at the base of the pile, or
• Dump and load-out in separate areas.

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DUMPING SHORT - Heres an example of dumping
inside the berm...
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Then pushing the material over the edge.
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DUMPING SHORT - Heres another example. In
this case the toe of the pile is being loaded
out, and the truck dumps back from the edge. A
good rule of thumb is to dump one-truck-length
back from the edge.
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And the material is pushed over by a dozer.
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DUMPING AT BASE OF A STOCKPILE. Keeps the truck
drivers from being exposed to the unsafe area at
the top of the pile. When loading a customer, a
good practice used at some operations is to use
the first bucket of material to block the
stockpiles access ramp. This prevents trucks
from going to the top of the pile until the
loader operator ensures that over-steepened
material has been pushed down and an adequate
berm is in place.
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SEPARATE DUMPING AND LOADING. Here, the dumping
and loading activities are separated. Once the
top surface had been covered, the piles will be
struck and another layer added.
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More on Dump-Point Practices

• Use the berm as a visual indicator only, do not
  routinely use it, or rely on it, to help stop the
  truck.

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Near the edge of a pile, trucks should back
slowly and come to a gradual stop. Putting on
the brakes abruptly imposes additional downward
and outward forces that could help cause the edge
to give way. Drivers should use the berm as an
indicator for where to stop, rather than...
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Hitting into and riding up on the berm. The
truck could go through the berm (especially if
the berm has been undercut), or the extra force
could cause the edge to give way.
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More on Dump-Point Practices

• Use the berm as a visual indicator only, do not
  use it or rely on it to stop the truck.
• Keep the dump area properly graded.

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• Grade the dump area so that trucks are backing up
  a slight grade to dump.
• This has the advantages of
• providing the driver with better control as the
  truck is backed to the the dump point
• putting the truck in a better position to be
  pulled forward if a problem develops, and
• keeping the dump area better drained.

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Keeping the dump area graded level from
side-to-side, and free of soft spots, will help
prevent trucks from tipping over as the bed is
raised. This is particularly a concern in cases
where material sticks in the truck bed.
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More on Dump-Point Practices

• Use the berm as a visual indicator only, do not
  use it or rely on it to stop the truck.
• Keep the dump area graded properly.
• Back perpendicular to the berm - not at an angle.

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Back trucks square to the edge of the slope as
shown on the left. In many dump-point accidents,
it is found that the truck had been backed as
shown on the right. In these cases, the longer
distance to the berm on the drivers side may
lead the driver to power the opposite-side rear
tires through the berm.
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Heres an accident where a truck went over the
edge of this spoil pile and the tire tracks are
at an angle to the edge of the pile.
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This is where that truck ended up, with fatal
injuries to the driver.
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OTHER DUMP-POINT HAZARDS

• Working at night or in poor visibility conditions.

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Provide sufficient lighting so that hazardous
conditions, such as cracks or inadequate berms,
can be detected during night operations. When
visibility is poor, a good practice is to dump
back from the edge.
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OTHER DUMP-POINT HAZARDS

• Powerlines.

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Best Practice is to locate any type of dump point
away from power lines or to have the power lines
high enough that they are safely above even the
raised-bed height of the haul trucks. Power
lines can also be marked to make them more
conspicuous.
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For more detailed information on dump-point
safety, consult MSHAs Dump-Point Inspection
Handbook. Lists of Best Practices from this
handbook, broken down for Mine Operator, Truck
Driver, Dozer Operator, and Front-End Loader
Operator, are shown in the following slides.
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(Mine Operators 1 of 3)
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DUMP-POINT SAFETY BEST PRACTICES I. MINE
OPERATORS - continued
(Mine Operators 2 of 3)
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DUMP-POINT SAFETY - BEST PRACTICES I.
MINE OPERATORS - continued
(Mine Operators 3 of 3)
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(Truck Drivers 1 or 2)
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Dump-Point Safety Best Practices Truck Drivers
- continued...
(Truck Drivers 2 or 2)
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By following the Best Practices, these
dump-point accidents could have been prevented.
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A complete copy of MSHAs Dump-Point Inspection
Handbook can be found in the FOIA Reading Room
on MSHAs web page at www.msha.gov.

• These related safety videos are available from
  the National Mine Health and Safety Academy
  (304-256-3257)
• -- Dump-Point Safety Stockpiles and Waste Piles,
  VC-858, 1997, 14 minutes.
• -- Good Berms Save Lives, VC-928, 1998, 15
  minutes.

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Additional Information

• Mine Safety and Health Administration
• Mine Waste and Geotechnical Engineering Division
• Stan Michalek, Chief
• (412) 386 - 6974

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